Hi, and welcome. Im extremely critical when someone asks for a critiquing. sooooo Im guna say what i think.
First off the best part of the boy riding the bike shot is the sunset, the reason Im saying this is because a huge silhouette doesnt do much for a picture mainly in the sense it doesnt evoke an emotion. I think that a sunset with a silhouette of a mountain. farther in the distance would be much much better. I really think the baseball pitcher is a good picture because you have your subject doing something that the common person couldnt do...not that that makes a picture good but it helps. next the boy jumping in to the pool is a little blurry just like Efergoh said so take that advice to heart.